It's a productivity method named after Jerry Seinfeld. I first heard about it from this lifehacker post: http://lifehacker.com/281626/jerry-seinfelds-productivity-se...

Basically you decide to do or practice something every day. If you forget or otherwise fail to keep up, you mark it in red on your calendar. Goal is to try to see how long you can go without a red mark. And get things done in the process.